Slalom focusing structures



June 14, 1960 Filed Jan. 9, 1958 2 Sheets-Sheet 1 FIG. /,4

//vv/v TOR J. S. COOK ATTOR EV June 14, 1960 J. s. COOK SLALOM FOCUSING STRUCTURES 2 Sheets-Sheet 2 Filed Jan. 9, 1958 INVENTOR J. S. C 00/\ M/Z? ATTORNEY United States Patent" 2,941,114 SLALOM FOCUSI NG STRUCTURES John S. Cook, New Providence, N.J., assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Filed Jan. 9, 1958, Ser- No. 707,916 1s Claims. Cl. 315-35 This invention relates to electron beam focusing arrangements and, more particularly, to apparatus for controlling the broad dimensions of a sheet or ribbon beam.

In United StatesPatent 2,857,548, issued October 21, 1958 of R. Kompfner and W. H. Yocom, there is disclosed an electrostatic focusing structure for ribbon or sheet beams which does not require the longitudinally time constant, spatially alternating fields commonly used in electrostatic focusing arrangements heretofore. Rather, there is disclosed in that application a structure comprising two spaced planar conductive plates with a longitudinal array of spaced positively biased conductive elements positioned intermediately therebetween. This structural arrangement gives rise to a pair of singular equipotential surfaces which wind sinuously past the linear array of conductive elements. These surfaces substantially form the trajectories for the electrons in the beam, provided that the electrons are injected substantially along one of the surfaces at the correct velocity which is dependent upon the specific geometry of the electrode system and the voltages applied thereto. The charged particles once having been projected along either of the two equipotential surfaces continue substantially along that equipotential surface inasmuch as the counteracting electrostatic and centrifugal forces are in balance. Such a focusing structure has become known as the slalom system since the electron beam follows a sinuous path through the linear array of conductive elements in the manner of a skier in a slalom race.

While slalom structures have proven very successful in containing the thickness dimension of a ribbon beam, the technique usually employed for containing the width, or broad dimension, of such a beam in a slalom structure has not proven to be completely eflective. This results from the fact that the beam edge focusing systems normally employed heretofore inherently limit the otherwise effective usable beam Width for a given dimensioned slalom structure which, correspondingly, prevents optimum beam focusing and circuit efiiciencies to be realized, the reasons for which will become more apparent hereinafter.

The beam edge focusing structure most generally employed in slalom systems heretofore has comprised two longitudinal edge plates extending from the slalom focusing planar side plates toward the linear array of conductive elements, being spaced apart a distance somewhat wider than the broad dimension of the beam. These edge plates have either been of insulative material so as to support the linear array or have comprised conductive members parallel to but isolated from the support members. In the latter case, a small gap on either side of the individual elements of the linear array has usually been employed. In either of the above-mentioned systems, the beam edge focusing members are at a negative potential with respect to the conductive elements of the array; this potential has been established in the case of insulative members by electrostatic charging and in the case of conductive membersby a direct negative poten "ice tial applied thereto. An electrostatic field is thus established between the beam edge focusing members and the individual elements of the linear array, the greatest con-- centration of transverse lines of force being established therebetween immediately adjacent the ends of the conductive elements of the array. This arises from the fact- 1 that in a slalom structure, as will become more apparent hereinafter, the transverse component of the electrostatic field between the planar side plates and the linear array decays from a maximum directly above and below the individual elements of the array, where the singular equipotential surfaces are furthest removed from the axis thereof, to a minimum intermediate adjacent elements of the array where the equipotential surfaces cross the axis thereof. Accordingly, with the two beam edge focusing plates being much closer in proximity to the edges of the linear array than are the planar side plates, the electrostatic lines of force bend outwardly to the inner sur- 1 faces of the beam edge focusing plates rather than ex- 1 tend between the elements of the array and planar side plates in a uniform manner laterally across the entire length of the individual elements of the array. This bending or distorting of the lines of force near the ends of the individual elements of the array results in the longitudinal edges of the singular equipotential surfaces bending inwardly in these regions where they are furthest removed from the axis of the linear array. This type of distortion results in the otherwise effective beam width being considerably reduced.

A reduction in the effective beam width directly afiects the efiiciency in discharge devices incorporating such a beam focusing system. More particularly, the etficiency is lowered since a particular transverse field configuration is required in order to constrain the ribbon beam thickness along the structure. Accordingly, if such a field is distorted by a concentration of the electrostatic lines of force between the beam edge focusing side plates and' the ends of the individual elements of the linear array-, an appreciable portion of the beam energy near the edges of same may be diverted to, and dissipated in the form of heat upon, various parts of the focusing structure. Correspondingly, in slow wave circuits, when the eifective width of the beam is reduced, the maximum surface area capable of being in coupling relation with an electro- In one embodiment of my invention, there is provided a longitudinal array of linearly and uniformly spaced conductive elements. These elements, which for con venience will often be referred to as wire-like hereinafter, even though other than cylindrical shapes may be equally effective, are supported at their respective ends by two edge plates normal thereto and spaced apart a distance slightly greater than the width of a sheet beam" which is projected along the array. Two planar plates are positoned equidistant from and on'opposite sides of the linear array of conductive elements. With suitable potentials applied to the linear array of conductive wire-like elements and the planar plates, transverse electrostatic fields are established which will, with the proper electron beam velocity, substantially contain the thickness dimension of a sheet beam initially injected along one of the two singular equipotential surfaces. In analyzing the behavior of,"a1id effects resulting Patented June 14,1960;

likeelements'areattached;'

In still another embodiment. of: my. invention, two beam 7 from, slalom focusing, I" have determined that optimum beam edge focusing is realized when the beam edge focusing field is either uniform or concentrated inter- .mediate adjacent elements of the linear array.- Advert-,

tageously,. in the latter case, as. pointed out above; it is' in these intermediat regions where the transverse electrostatiofield'between. the linear array and'planariside plates is: minimum. Accordingly by positioningv suitQ able 'beam edge focusing elements in theselintermediate regions, in accordance with the principles of; this inven tion, distortion of the transverse electrostatic fields along, 7 a

theedges ofthe arraywill'be minimizedwith-a consea quent increase in eiiiective beam widthand. focusing efiigiency realizedtherefromi In accordance with one; aspect of my in ention in one embodiment thereofithe width or broad dimension; of. a-sheet-beam projected along, a slalom structure is con tained by :an-i electrostatic field{ establishedbetween a linear array of wire-like-elements and. a plurality of short;- conductive stubs isolated from, but extending through the edge plates of the slalom structure intermediate the spaced conductive elements of the linear array. These short conductive stubs areattached to two side wall support members whichare insulated from, but.

adjacent to and extending parallel: with the edge support: plates to which the parallel array of wire-like elements are attached- Advantageously, these conductive stubs with the; proper. potentials applied thereto, effectively concentrate-the beam edge focusing field along a short'longitudinal region on either sideof, the cross-over point the latter being defined asthat pointwhere the two singular equipotential surfaces crosseachother intermediate'the; array of spaced conductive elements. It is in: these regions where the transverse, component ofthe electrostatic field between: thefllineararrayand planar.

sideplates is Accordingly, the. presence of these-focusing stubs in a-slalom. system will not appre ciably; afiect the electrostatic: lines: offorce which .estab-' lish the singular equipotential surfaces as is occasioned with previously known :beam edge focusing elements that proximity 'to*th'e edges ofra sheetihe'am' in aslalomJstIuct ture-for establishing a. beam e'd ge focusing field 'which has a concentrated field ot'fl'ux at least as; great in :the

regions intermediate adjacent elementsof a...linear array as in the regions immediately adjacent the elements of suchanarray. V i 1 V a 7 'It is another feature of this invention to utilize beam edge focusing elements which are insulated from and biased independently ofithe edge plate supportmembers for thelliheaiiarray; f a V A. complete understanding; of. this. invention. andI the various features thereof may be gainedf'romrconsidration of the following detailed description-and; the accompanying drawing, inwhich 1.

Figs 1A and 1B areschematic representationsjofltlie electrostatic field and; singular equippt'ential surfaces in V a conventional slalom focusing structure;

Fig, 2 is a perspective cutaway view ofonev illustrative embodiment of an electron heam system utilizing slalom a focusing andincorp'oratingthe beam edgefocusing features-of the. present invention;

Figs. 3 through ,5 are partial perspective views illustratingf various otherembodiinents of-"the beam edge 1 focusing structure of myinvention, depicted in Fig.,.2;;

arerpositione'd continuously alongthe edgesof the slalom structure.

In ,c'ertainiothert of the embodiments of this. invention,

the; electrostatic. beam edge focusing elements comprise a.- plurality-of vertical fins or wires which extend trans. verselyfromeither or both of the-planar plates. These Wires .or fins are positioned; intermediate adjacent wire= like elementsof the array and in close: proximity'to but isolated from the support members to which thewireedge, focusing; plates extend longitudinally along; the sides lof-a ,shee't beam and-are apertured for passage of thelinear array; of wire-like elements; therethrough, the;

diameter-10f theiapertures. beingconsiderably larger than the. diameter of the conductive elements of the array.

As described in greater detail hereinafter, this resultsin theuelectrostatic. beam edge focusing fields having the greatest number of linesof' force'in a regionbetween adjacent apertures. and the respective ends of the con zductive'elemehts of. the lineararray. With such a focusingarrangement, as with the previously mentioned minimized.

a In still anotherembodiment of my invention, two thin.

barmagnets serve asithe planar side plates and. are magnetized-inn direct-ion normalto the path of electron flow, but ,aregof opposite polarity along their respective longi- .tudinal edges. Accordingly,qthe magneticfield estaband , Fig. 6 a cross-sectional perspective'view of stillanother illustrative embodiment "of a beam edge focusing.

structure which utilizes a magnetic focusingfield.

Referring now to the drawing, Fig. 1A is'a schematic representation of the electrostatic lines of force 8.which exist between a linear array of conductive elements 12 and planar side plates 13 in a slalom structure- As is' well known, the electrostatic lines of'force 8 are always" at right angles'to the various singular equipotential surfaces 9 that may exist. If is seen by the cyclical variations in the number of linesof force 8'that exist'be tween the linear array '12 and planar side plate 13, hereinafter spokenof as the transverse component, that the greatest concentration of lines of force. therebetween are established in those regions directly above and below the individual elements of the linear array. In thosetre'gions intermediate adjacent elements of the array, the trans verse component of the electrostatic fieldzis minimum:

embodiments, distortion of the edges of the singular. 7 equipotential surfaces which are furthest removed from. theaxis of thelinea'r array of wire: elements .Will be lishefdqbetween-these side-.plates. effectively. contains the: A

broad; dimensionofa sheet beam which maybelconsiderably wider than was possible; heretoforeina given 'difnensional Ri-E. slalom structure. p

.stantially reduced j v V g i 1 Accordingly, :I have discoveredthat by positioning elec ostat e asin 7 e in eme s n. thes e s-1 Accordingly, in those regions, wherethe transverse component of the electrostatic field isQmaximum, the sinuous" singularequipotential surfaces are furthest removed from: theplane of the linearlarray, and in those regions Where the. transverse component of 'the. field is minimum, the equipotential surfaces cross the plane of the lineararray;

Fig..1B.is a schematic representation incrosslsection showingvthe'efi'ect. that one typegof conventional beam edge focusing.structure comprising members 33, described above, have upon the. longitudinal edges; of the. equi potential surfaces. Since. these beam edgefocusingmemhers, which may alsoserve as supportsfor the wire-like elements insulatcd'therefrom, are ata negativepotentialwithrespect to. the wire-like elements of the linear array, usually being at the potential of thepl'a'nar side plates 13, a highly concentrated electrostatic field is estab lisheditherebetween. .The resultant bending or distortingoflthe.equip otential surfaces, because of the nature of the" conventional beam edge focusing members 33,..results in the othenwise eifective beam"width bein g subintermediate adjacent wires of the linear array where the electrostatic field is minimum, and by aligning these elements a short distance inwardly along the longitudinal boundaries of the wire support members, the distortion along the longitudinal edges of the equipotential surfaces may be minimized and increased beam width realized therefrom.

The illustrative embodiment of this invention shown in Fig. 2 comprises an electron beam tube enclosed within an evacuated envelope 11, which may be of glass. Extending longitudinally within envelope 11 is a linear array of uniformly spaced conductive wire-like elements 12 which are transverse to the axis of envelope 11, these elements being positioned between and equidistant from two conductive planar side plates 13. Each of the wirelike elements 12 is maintained at a positive potential with respect tothe two planar side plates 13, such as by battery source 24.

In accordance with an aspect of this invention, a plurality of conductive stubs 14 extend from two longitudinally extending support plates 15 and pass through two wire support members 16 from which they are isolated. These conductive stubs 14 are positioned intermediate thelinear array of wire-like elements 12 and in alignment therewith. Advantageously, this permits the Wire support members 16 to be at the same potential as the individual wire-like elements which they support. -Acc0rdingly, with a potential applied to the conductive stubs 14 which is either equal to or slightly less than the planar side plates 13, an electrostatic field is established between the conductive stubs 14 and the wire-like elements 12 such that the greatest concentration of beam edge focusing lines of force is realized in the regions intermediate the ends of adjacent Wire-like elements 12. In this way, the two singular equipotential surfaces are not distorted near the edges, as defined by the distance between corresponding opposite ends of stubs 14, by a crowding of the electrostatic lines of force as is normally experienced with previously mentioned slalom structures.

An electron source 18 is positioned intermediate two adjacent wire-like elements 12 near the left-hand side of envelope 11, as viewed in Fig. 2. Such an electronsource is specifically disclosed in the aforementioned patent of R. Kompfner and W. H. Yocom. Briefly described herein, such an electron source comprises a filamentary cathode 19 extending parallel to the individual wire-like elements 12 and surrounded by..an anode 20. Advantageously, the anode is positioned at the cross-over point of the two singular equipotential surfaces associated with the linear array so as least to affect the potential distribution in the interspace and particularly the singular equipotential surfaces. The anode Zil is slit such that a sheet beam is injected substantially along one of the desired singular equipotential surfaces and with the correct velocity, will have a trajectory substantially corresponding to the singular equipotential surface, the sinuous path of which is identified by the broken lines 17.

Alternatively, in certain applications it may be desirable to utilize an external cathode to inject an electron beam along a trajectory substantially following a singular equipotential surface, as taught in the copending application of J. S. Cook, R. Kompfner and W. H. Yocom, Serial No. 514,421, filed June 10, 1955.

i The electrons are collected by a target electrode 21 positioned at a point along the path of flow beyond which the beam has completed its desired function for the particular application intended. This target electrode includes a collector housing 22, which is slit in much the same way as anode 29 of the electron source, with a target collector 23 being axially positioned within the collector housing 22.

For simplicity and convenience of illustration, a slalom structure comprising only a simple linear array of wire-like elements 12 is disclosed in Fig. 2. As previously mentioned, however, a slalom focusing system readily lends itself to beam type switching tubes, as disclosed in United States Patent 2,899,597, issued August.

11, 1959, of R. Kompfner, or a slow wave interdigital R-F circuit for use in traveling wave devices, such as disclosed in the aforementioned patent of R. Kompfner and W. H. Yocom.

The manner in which operating potentials are supplied to the circuit is schematically illustarted by lead-in connections shown from the battery source 24 to the vari ous elements of the device. The cathode 19 and'the planar side plates 13 are maintained at the reference level, which may be ground corresponding to the negative terminal of voltage source 24. The accelerating anode 20 and the target collector housing 22 are advan' tageously maintained at slightly higher positive potentials than are the cathode. 19 and side plates 13.' The 1 target collector 23 within the housing 22, as well as the: wire-like elements 12 of the linear array and their support members 16, are maintained at the highest positive potential with respect to the reference level, this cor responding to the most positive terminal of voltagesource 24. 1 In accordance with an aspect of this invention, the

beam edge focusing stubs 14 are maintained at a potential considerably less positive than the wire-like ele ments 12 of the linear array and planar side plates 13,

but slightly more positive than the cathode 19. This.

results in the electrostatic field established between the wire-like elements 12 and focusing stubs 14 being the only beam edge focusing field that exists and it is concentrated intermediate the wire-like elements 12. Advantageously, the conductive stubs 14 extend inwardly from the support members 16 a distance which assures that the longitudinal edges of the beam will not be affected by any bending or distorting of the transverse lines of force between the support members 16 and the planar side plates 13 in thoseregions of maximum transverse field. While such distortion is not appreciable in the beam edge focusing arrangement depicted in Fig. 2, it could be further substantially reduced, if desired, by making the support members 16 of insulative material. The individual wire-like elements 12 would then be connected directly to the voltage source or through a con-v ductive member extending longitudinally along the outer side of either or both of the insulative support members. Alternatively, the outer conductive members could be utilized to support the array and the insulative mem-. These.

bers would act merely as electrostatic shields. modified structural arrangements could similarly be employed in the focusing structures depicted in Figs. 3 and:

4, as it is in Fig. 6, all of which are described in detail hereinafter. Since, in either case, there is no potential drfl erence between the ends of the wire-like elements 12 and their support members 16, the singular equipotential" surf aces wrll not be distorted by a concentrated electro-. statrc field therebetween as experienced heretofore'and as illustrated in Fig. 1B.

Fig. 3 shows a partial sectional view of an alternative beam edge focusing arrangement. For convenience, structural elements which are similar to those appearing in Fig. 2 will be designated by corresponding reference scribed hereinafter.

depicted in Fig. 2, permits the support members 16 to be at the same potential as the wire-like elements 12.;

Further, since the transversely extending wire elements 25 are attached to either one of the side plates 13, they may be positioned intermediate the previously and independently fabricated linear array of wire-like elements 1116135525 depicted; in: Fig.3.

.wire-like' elements; 12;

structure.

' :41 is: amodificatioirof the structurerillustrated ini Fig: 32;: being distinguished therefrom by a plurality-jofi; fins' 26 replacing the transversely extending'wire" ele- .Theutilization of fins rather thanswires as-the focusing. elementsin Fig..4.pro-

a' more, rigid. structuralarrangem'ent with. equal.

beam edger focusing characteristics being; realized there.-

" ItJshOuId. be noted. alarm. both Figs. 3'- as 4 the focusing elements. do not extendinwardly an. appreciable distance which would. tend to impair the usable beannwidtlrfor agiiven dimensionedlstrhcture: By: way... oiiiexample,- the; fins 26,. depicted in. Fig. 4; might .extend inwardly approximately one=twelth of the'dist'ancei between the:edge-.supportmembers 13. These-focusingmlei ments have: been made to; appear considerably largerin theidrawingszforl purposes of. better illustration As pro-j viously mentioned, the: important. requirement that:

the beam edge focusing elements depicted ind-Figs. 2.

throughi l", .whiclr'define the. elfective' usable.beam;width, should. be. longitudinally aligned inwardly. from the sup-- port. members 16, a distance suchxthatianyi bendingj'of.

' the transverse lines of forcebetween the. support meme hers 16.and; planar side plates: 131 WillaHOt appreciably V affect'thefocusing along the edges ofthe'beam.

Fig. Sis a. partial sectional view of'still anothertbeazn tor'members 31 may advantageously be. employedto support the bar magnets: 29. It is particularly advantageous" in this. structure: to utilizeztinsulative material for the sup port members 15; Inv certain; slow wave R.-F." circuit application's, two-conductive planar side plates 32 may; be. advantageous for purposes of securing .a; particular propagation characteristic as well as for structural-reasons.

' Such. a beam edgefocusing; arrangement p'ermits a high current, high density sheetbea'm having a'width just slight ly less than the distancewbetweenthe insulative wire like support members 16 to.:be.;effectively focused .alon'ga' slalom'course- Highbeam 'efiic'iency isalso assuredi since distortion. of: the singular equipoten'tialv lines,; which: the beam-substantially follows, is minimizednear. the; edges because: of. the; uniform. beam: edge; focusing. fieldfandi becausez-ofithe insnlative character of. the, support .mem bers 1d withirespectstcr bothithe wire-like elements. 12; and the planar side plate bar magnets 29:" Potentials could be? applied. to theaindividual: wire-'lflr ezelements; by

edgefocusiirgarrangement in accordancezwiththeprineciples of.my:invention.. In placeofthe various conduc:

tive beam edge focusing: elements. depicted. ii1:.'Figs..2: through 4,.beam;edgeiocusingcplates 271' are utilized and characterized by having apertures. 28 therethrough; for

passage of;.therwiie-like: elementsi 1L Thesefocusing plates. 27 may be at; the: samepotential as'the condue trve? beam. edge. focusing stubs depicted in Fig; 2;. In. 361 corrlanceiwithv an'aspect of thisiinventiomthe' apertures.

- 28fthrough the beamedgefocusing plates 27 are of a diameter substantiallygreaterthanthe diameter ofthe Advantageously; this: forces? a concentration of. efiective beam: edge focusing: lines of force. to be: established: between. the ends of the wire- :like elements 12 and those 'regionstofthe focusing plates- 21 intermediate: adjacent apertures 28; With tbis arrangement, a. sheet heaimmay havel a width just-slightly less. than. the. distancebetween the beam. edge focusing plates'27. I i j a In Fig; '6 a cross; section. of a'. magnetic edge focusing. system is illustrated for: containing. the. widthrofi a sheet beam ima; slalonnstru'cture; In place :of'the eon.-- ductive: planar. side. plates. 13,. which bound the: linear direct leads: thereto. or through conductive'i edge" mem here which could also be utilized as thBlWltQ-likfi sup:

ports: in a manner similar to. members" 16 depicted: in

Fig. 5;

7 It is tobeunderstood that the specific. embodiments.

' described herein are merely illustrative. of the. general.

principles of the present-invention. For example, in place v of the conductive beam edge focusing-elements disclosed-- herein; a sinuous conductive sheet could extend longitudi n'ally along the respectiveedges of the: linear arrayof wire-like elementsand would provide an equally 'e'fiective: beam edge" focusingasystem. Similarl'y in'placeof the side plate:- permanent bar' magnets, twoferrite sideplates';

could be utilized with a-thin metallic coating on" thednner surface and" along theirrespective edges so as to afford a means for establishing the'proper' electrostatic' and magneticnfiel'd relationships desired; Further; beam ed'gefocusing elements such as depicted in- Figs; 2 through 4 could beof a- -suitablednsulative material"; this' permitting electrons near the edges of thebeam 'to impi'nge 4 upon and charge electrostatically-these elements to'the proper biasing potential. Various other struc'tura-l arrangernents and 'modfiications may be similarlydevised in the light of this': disclosure ,by'one skilled 'in them; without-departing from the spirit" and scope or; thisp'in' vention. I

What isclaimedisr l V g g ,7 lfAn electron beam system"comprising a spao'ed pair of planar conductive bounding meansga plurality of spaced conductive elements' forming-a linear array which extends longitudinally. in the: interspacebetweerr said planar conductive bounding'means, means f'or biasing" the array. as disclosed inFigsrZ throughiS, there'are utilized this manner, the proper force relationships are established and characterized in. thaLsuch a field is uniform along the respective edges of the linear array of wire-likeelements' 12'. Further, V to minimize leakage fiux andi'to as} sure maximum concentration efilux along" the respective In other edges of a sheet beam; the side plate bar magnets29"advantageously have rib-like protrusions 3% which extend inwardly toward each other a 's'hort dista'nce' and 'fur la. desired'magnetic' flux path .therebetwe'en: if is :this feature which permits a beam-of maximum width for agiven dimensioned slalom structure to be: effectively focused with a. minimum of. magnetic; fieldi intensity;

lineaiarray: in the same manner. as. theiplanar, side plates? described above: in regard tdFig. 2.. T-woz-thinyinsnlagf15- elements Withrespectjto said 'planan conductive bound-- ing means for establishing a pair'ofsingular equipotential surfaces which, extend longitndtnailyalonglancf wind sihuouslypast the" elementsofsaijd array, means for pro"- jecting an electron beam substantially alongatv least one of said equipotential surfaces, andinreans forecofining the edges of said beam, said last menti'oned means including at least two beam. edge. focusing elements positioned in close proximity to the edges 'ofsa'idg'bearn for establishing a concentrated'field of 'beamed'gefocus'ingj flux at least as great in. the regions intermediate adjacent. elements ofssaid array as inthe regions immediatelyad jacent the elements of saidarray. 1 2. An. ele'ctronbeam system in accordance 'withclaim 1 wherein saidbeam edge "focusing; elements comprise for passagelofthe elements ofsa'idarray therethrough and 7 biased with respect. to theelements of said, array such.

7 These banmagnetsare also. biasedwithirespeetto: the.

that the greatest concentration of'beam edge-focusinglines of-force exists between the elementsofsaid' .array: and" the regions intermediate adjacent apertures of said longi tudinally extending edge members. r

i 3. An electron beamsys teminaccordance with claim 1. wherein said beam; edge. focusing element'sv comprise 9 longitudinally extending rib-like protrusions facing inwardly toward the linear array and defining the outer edges of the path of electron flow, said rib-like protrusions forming the respective poles of bar magnets and arranged such that adjacent edges of said rib-like protrusions are of opposite polarity for establishing a uniform and concentrated magnetic beam edge focusing field therebetween.

4. An electron beam device comprising a longitudinally extending focusing electrode system which establishes two sinuous singular equipotential surfaces having at least one point of intersection, an electron source and collector positioned at opposite ends of said focusing electrode system for projecting a ribbon beam therethrough and substantially along one of said singular equipotential surfaces, and means for containing the width dimension of said beam comprising at least two beam edge focusing elements positioned in close proximity to the edges of said beam, said focusing elements establishing a concentrated field of beam edge focusing flux at least as great in the regions near the edges of said equipotential surfaces where said surfaces intersect as in those regions where said equipotential surfaces are furthest removed from the common axis thereof.

5. An electron beam device in accordance with claim 4 wherein said beam edge focusing elements comprise a plurality of conductive elements positioned near the longitudinal edges of said focusing electrode system and spaced uniformly therealong at points coinciding with those regions at which the equipotential surfaces intersect along the common axis of said sinuous paths, and means for establishing a potential difference between the longitudinally extending focusing electrode system and said beam edge focusing elements such that a concentrated electrostatic field is established therebetween for effectively containing the broad dimension of said ribbon beam.

6. An electron beam device in accordance with claim 4 wherein said beam edge focusing elements comprise two longitudinally extending conductive side members which define the effective beam width along said longitudinally extending focusing electrode system.

7. An electron beam device comprising a longitudinally extending linear array of conductive elements, a pair of planar conductive side plates extending longitudinally an equidistance of either side of said array, means for biasing the elements of said array with respect to said side plates for establishing a pair of singular equipotential surfaces which extend longitudinally along and wind sinuously past the array of elements bounded by said side plates, means for injecting an electron beam onto at least one of said equipotential surfaces, means for collecting said beam, and means for confining the edges of said beam, said last-mentioned means including a plurality of conductive beam edge focusing elements positioned near the ends of and intermediate adjacent elements of said array and means for biasing said focusing elements with respect to said linear array for establishing an electrostatic beam edge focusing field therebetween which has the greatest concentration of lines of force in the regions intermediate the elements of said array.

8. An electron beam device in accordance with claim 7 wherein said beam edge focusing elements comprise a plurality of short conductive stubs extending inwardly fi'om at least one side of said linear array intermediate the elements of said array and in alignment therewith.

9. An electron beam device in accordance with claim 7 wherein said beam edge focusing elements comprise a plurality of short conductive members extending transversely from at least one of said side plates and positioned intermediate adjacent elements of said array and in close proximity to the outer longitudinal edges of said array.

10. An electron beam device in accordance with claim 9 wherein said transversely extending elements are in the form of wires.

11. An electron beam device in accordance with claim l 10 l 9 wherein said transversely extending conductive members are thin conductive fins with the broad dimension being in alignment with the elements of said array.

12. An electron beam device comprising a plurality of spaced conductive elements forming a linear array, means for biasing said linear array of elements with respect to means bounding said array for establishing two singular equipotential surfaces which extend longitudinally along and wind sinuously past the elements of said array, an electron source and collector for projecting a ribbon beam through said linear array of elements with at least one of said equipotential surfaces forming the trajectory along which the electron beam will substantially traverse, and means for confining the edges of said ribbon beam, said last-mentioned means including said means bounding said array which comprises two thin bar magnets having a magnetic axis transverse to the desired direction of electron fiow and positioned such that adjacent longitudinal edges of said bar magnets are of opposite polarity for establishing a uniform and concentrated magnetic beam edge focusing field therebetween.

13. An electron discharge device utilizing slalom focusing comprising a longitudinally extending array of conductive elements, a pair of planar conductive side plates extending longitudinally an equidistance on either side of said array, means for projecting a fiat electron beam to wind sinuously past the array of elements bounded by said side plates, means for collecting said beam, and means for confining the edges of said beam, said lastmentioned means including an outer edge plate to which said conductive elements are attached and an inner edge plate having apertures therein through which said conductive elements extend.

14. An electron discharge device utilizing slalom focusing comprising a longitudinally extending array of conductive elements, a pair of planar conductive side plates extending longitudinally an equidistance on either side of said array, means for projecting a flat electron beam to wind sinuously past the array of elements bounded by said side plates, means for collecting said beam, and means for confining the edges of said beam, said last-mentioned means including an outer and an inner edge plate and a plurality of short stub members projecting intermediate said conductive elements, one of said stub members and said conductive elements being attached to the outer and the other to the inner edge plate.

15. An electron discharge device utilizing slalom focusing in accordance with claim 14 wherein said conductive elements are attached to said inner edge plate and said stub members to said outer edge plate, said inner edge plate being apertured for passage therethrough of said short stub members.

16. An electron discharge device utilizing slalom focusing in accordance with claim 15 wherein said stub members are positioned equidistant from adjacent conductive elements and in alignment therewith.

17. An electron discharge device utilizing slalom focusing comprising a longitudinally extending array of conductive elements, a pair of planar conductive plates extending on either side of said array, means for applying slalom focusing potentials to said conductive elements and said plates, means for projecting a flat electron beam to wind sinuously past the array of elements bounded by said plates, means for collecting said beam, and means for confining the edges of said beam, said last-mentioned means comprising conductive means positioned midway between adjacent of said conductive elements and aligned 'with said elements and means for applying a potential to said conductive means negative with respect to the potential of said conductive elements.

18. An electron discharge device utilizing slalom focusing comprising a longitudinally extending array of con ductive elements, a pair of planar conductive side plates extending longitudinally and equidistant on either side of said array, means for projecting a fiat electron beam to sinuonsly 'QflSt am yci elements boundcd; by aid 'sidefpla s 'mcans for. ccll t d eam, and fi1eansfor confining the, edges of said beam, said lastmentioncd means comprising magnetic means positioned directly adjacent the endscfsaidconductiyeelements and having a magnctic faransverse to thedi iectipn of said electron beam f0: establishing a uniform aind concen "mated magnetic. beam edge focusing, field solely in -th e vicinity of said conductiverelement .ends.

12 Bcicmnsc Cit d. I112 file. oi, 1 ml N UNITED STATES-PAT TS Hehlgans Dec. 18, 19 34 LQ n p 22, l Adler r; .,l Oct. 8, 1 957 Gueuard pt :11. Mar. 18, 1958 K'ompfner Oct, 21, '1958 F E GN PATENT France Aug. 27, 1956 

